In recent years, a high-frequency semiconductor switch for use in a receiver circuit or a transmission circuit in the communications field has progressed in design to provide high performance and high functionality. Furthermore, cost reduction, miniaturization, and high integration have been strongly required in the design of the high-frequency semiconductor switch. To meet such a requirement, instead of HEMT (High Electron Mobility Transistor) or other compound semiconductor devices conventionally used, high-frequency semiconductor switches appropriately using Silicon on Insulator (SOI) type Metal Oxide Semiconductor (MOS) transistors with smaller parasitic capacitance and smaller electric power loss than MOS transistors formed on silicon substrate, have been developed. For the SOI type MOS transistors formed on SOI substrate, multiple circuits can be easily formed on the same substrate and thus on one chip. For example, high-frequency semiconductor switch circuits, such as a serial-parallel conversion circuit, a power supply circuit, a drive circuit, a switch circuit, and so on, can all be integrated on one chip.
For the high-frequency semiconductor switch chip integrated with multiple circuits, multiple high-potential power supplies are used. In the serial-parallel conversion circuit and other digital calculation processing circuits, independent high-potential power supplies are provided. In each of the various circuits, if the high-potential power supply is in a shutoff or disconnected state, an erroneous action of the switch circuit may occur.